The present invention generally relates to processes for machining materials. The invention particularly relates to systems and methods for improving the machinability of surfaces of relatively soft and/or ductile materials, such as but not limited to annealed metals and/or alloys.
A typical machining process involves removal of material from a body with a cutting tool. The portion of material removed from the body is commonly referred to as a chip, and under appropriate conditions may be in the form of a continuous chip. For example, FIG. 1 represents a cutting tool 12 in contact with and moving relative to a workpiece 14 to form and remove a portion 16 of the workpiece 14, referred to as a bulk material, to yield a chip 18. This example represents an ideal plane-strain machining process characterized by formation of the chip 18 by simple shear resulting in a smooth, laminar flow of the material.
It is well known that machining a non-brittle metal in a soft state, for example, after being annealed, is significantly more difficult than machining the same metal in a hardened state, for example, after undergoing strain hardening. When the workpiece being cut is a metal in a soft state, the machining process generally requires a relatively large cutting force and results in an unusually thick chip. This difficulty in cutting, well known in industrial practice, has hitherto eluded fundamental explanation. Conventionally, at the mesoscale (for example, about 100 μm up to about 5 mm), the structure of the chip has been assumed to be homogeneous, resulting from laminar plastic flow as represented in FIG. 1 (schematically represented by flow lines within the chip 18). Using such framework, augmented by ex situ observations, the high forces have generally been attributed to the thick chip developed in the process, without an explanation of the cause of such anomalous chip formation.
In view of the above, it can be appreciated that it would be desirable if methods were available for machining relatively soft and/or ductile materials with reduced cutting forces and thinner resulting chips.